Damping means for hydro-pneumatic oleo struts and the like



.505, .509, BB, BA, 96.2, .51. .9, 100? e ,Umted States Patent 11113,542,169

[72] Inventor .lohauel ortbell [56] References Cited 4151, UNITED STATES PATENTS [21] Appl. No. 769,114 7 461,347 10/1891 Krone 188/96.9UX 2 332 520 10/1943 1. 11: 188/96 9ux 4s Patented Nov. 24, 1910 1 [32] P it o 25 1967 2,575,389 11/1951 Lom1tzo l88/88BAUX 33] y h 3,111,201 11/1963 Bliven et a1. 1/8 s .509 1 625,330 3,215,426 11/1965 Engels l88/96.(9)X 3,445,103 /1969 l-lennells l88/96.(9)X

' Q FOREIGN PATENTS 1,076,192 4/1954 France 188/100(R) 1 Primary Examiner-George E. A. Halvosa [54] DAMHNG MEANS FOR "YDRoJNEUMA-"c Attorney-Holman, Glascock, Downingfi'seebold 01.110 s'riw'rs ANp r111: LIKE 5 Chum 3 ABSTRACT: A line of movement dependent damping means [52] US. Cl...... 188/285, for hydropneumatic oleo struts or the like in which a cylinder 188/ 100 has a' piston therein and a pressure reservoir or accumulator is [51] lnt.Cl. F161 9/32 operably connected with the pressure space of the cylinder [50] Field olSearch .L ..l88/88.502, having a damping characteristic variable as a function of the position of the piston relative to the cylinder.

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"Pat riterT N bQ. 2 1910 r i:- 1 1 Sheet 4p!) Fig. 3

W D V+M ATTORNEYS cludes a cylinder 1 in which a piston i 1 DAMPING MEANS FOR HYDRO-P EUMATIC OLEO STRUTSAND TII LIKE BACKGROUND OF INVENTION This invention relates to 'a' line of movement dependent damping assembly for-hydropneumatic oleo struts and the like. I

Such damping assemblies are used, for example, for the socalled end position dampings of cylinders and in such assem blies the piston is provided with an axially directed shoulder which moves in a corresponding bore in the cylinder and displaces the liquid present through the remaining annular space which becomes longer with an increasing pistonstroke. The

disadvantage of this particular arrangement is-that'the damping characteristic cannot be changed and moreover, the length 1 of the cylinder increases by the-length of damping.

Another darnping assembly of the aforementioned type is disclosedin German- Pat. No. 1,058,854 in which the wall of the cylinder provides a succession of axially spaced bores of decreasing diameter and as the piston moves Over the bores,

the remaining cross section for flow becomes increasingly smaller and the damping'accordingly more difficult. With this through the bores the structural dimensions of the assembly are increased.

SUMMARY OF INVENTION It is salient of the present invention to provide a strictly line of movement proportional damping assembly which permits adjustment and which assembly by being'comp act can be accornodated within-the dimensions of a common orcustomary cylinder unit.

The foregoing object is'realized by providing between the pressure space of the cylinder and a pressure reservoir-or accumulator, a spring loaded pressure limiting or; pressure gradient valve which opens towards the zreservoir, with the tension of the spring being variable by a displacement of a spring abutment corresponding to the relative movement between the piston and cylinder.

in a preferred embodiment of the invention, the pressure limiting valve is disposed within the cylinder and is constituted by a rod which extends axially into-the pressure space and which constitutes together with a piston slidable in a hollow piston rod and biased by a spring against the piston rod, a valve seat and the pressure reservoir or accumulator is operably connected with the spring zone or area.

The rod may be hollow and functions asmeans for providing communication withthe reservoir and a free flow from the reservoir to the pressure space can be effected by a check valve arranged in parallelism with the pressure gradient valve but opening in the opposite direction.

Further objects and advantages of v the invention will become more readily apparent to persons skilled in the art from the following detailed description and annexed drawings.

DESCRIPTION OF THE DRAWINGS FIG. 1 is a diagrammatic view illustrating the salient aspects ofthe invention, t v

FIG. 2 is a diagrammatic view illustrating the variationof the pressure differences to be overcome at different settings as a function of the stroke, and

P10. 3 is an axial sectional view of an embodiment of the invention.

DETAILED DESCRIPTION OF INVENTIO Referring to FIG. 1', it will be noted that the assemblage in- 2 is slidably mounted and is provided with a piston rod 3. The piston rod 3 by means ofa responding manner.

control means '4'variesthe initial tension of a spring 5 of a pressure gradient valve 6 which is connected to pressure space 7 of the cylinder 1.,The pressure space 7 via the valve 6 is connected with a pressure'reservoir o'r accumulator 8. A check valve 9 which opens in theopposite direction may be connected in parallel with the pressure .valve 6,

Referring now to FIG. 3, it will be noted that a piston 11 having a piston rod 10 is slidably disposed in bore 12 of a cylinder 13. A rod 15 the cylinder projects axially into pressure space 14 of the cylinder. The rod further extends into a bore 17 provided in the piston 11 and piston rod 10.

It will further be noted that the bore 17 merges with a bore 18 of larger cross section and the lower open end of the bore 18 is closed by an adjustable plug or closure 19. A piston 21 is mounted within the bore 18 and the piston 21 is held against a shoulder 22 by means of a helical spring 20 which has its respective ends bearing against the plug 19 and piston 21 respectively. Manifestly, the upper limit of the stroke of the piston 21 is determined by the shoulder 22.

It will further be noted that the head of the piston 21 is profice a reduced portion 24 of the rod 15 can project while a shoulder '25 surrounding the reduced portion 24 constitutes in conjunction with the piston 21 a valve seat. The rod 15 is provided with a bore 26 which extends throughout the length thereof and the upper end of the bore 26 is in communication with a hydropneumatic pressure reservoir or accumulator 27. It will also be notedthat in proximity to the base 16, the rod 15 is provided with a transverse bore 28 which is surrounded by a cuff 29 functioning as a check valve.

The" operation of the above-described assemblage is as follows:

Starting from the position illustrated in FIG. 3, the piston 11 moves in the cylinder 13 and liquid is displaced from the decreasing pressure space 14 into the reservoir 27 by means of the bores 17 and 26. The reduced portion 24 of the rod 15 moves closer to the orifice 23 of the piston 21 which of course is pressed against the shoulder 22 by the spring 20 under a certain initial tension. With the increasing approach, the remaining' hiatus between the piston 21 and'the rod 15 becomes smaller and the liquid which at first flows substantially without resistance is throttled more and more. This action results in a pressure increase in the pressure zone 14 relative to the spring zone or the bore 26 and the reservoir 27. As soon as the increase in force caused thereby and which acting on the top of the piston 21 exceeds the force of the spring 20, the piston 21 will move inwardly relative to the piston rod 10 and augment the tension of the spring 20 according to the stroke of the piston. As the force of the spring 20 increases in proportion to the line of travel, the resistance to flow increases in a cor- As is depicted in FIG. 2, the different damping characteristics can be adjusted-and this is achieved by means of the plug or closure 19. In other words, different initial tensions of the spring can be adjusted such as for instance, F being greater than F being greater than F The greater the initial tension, the greater at-equal strokes the necessary pressure difference AP. Another possibility of adjustment results by a displacement of the rod 15 andwith the rod 15 extending far into the pressure space 14'or the piston rod 10, the damping begins to become effective following a relatively small stroke h,. If the rod is moved out by an amount Ah, the damping sets in only at h? h +Ah.

Manifestly, it is also possible by a suitable dimensioning of the individual components to damp directly starting from a zero position. The initial pressure gradient then corresponds for example, to Apl or A p2. When, following a certain stroke, the piston 11 comes to rest, the shoulder 25 will be positioned on thehead of the piston 21 and thus constitute a tight seat or seal. Upon extension the seat is initially maintained and according to the movement of the piston the resilient zone again increases and the liquid requirement is supplied from the displaceably connected in a base. 16 of reservoir 27. The pressure space 14 is in part filled with the liquid displaced by the piston 21 from the bore 18 and the lacking liquid passes from the reservoir 27 by way of the bore 26, the transverse bore 28 and cuff 29 into the pressure space 14.

It is of course to be appreciated that other examples of structural arrangement are possible within the scope of the in vention. For example, the seat between the rod and the piston may be of other designs and flat or conical seats are feasible. To avoidany undesirable effects of viscosity, the orifice 23, may, for example, be conical thereby providing a sharp diaphragm type control edge, The rod 15 may be provided with a blind bore provided the reservoir 27 is connected in a different manner with the resilient area 30. Of course, the invention may be employed with plunger as well as piston rod cylinders and it is not necessary for the piston to be provided with a central orifice if it slides under the seal in the bore 18 and the resilient zone 30.

lclaim:

1. A line of movement dependent damping assemblage for hydropneumatic oleo struts and the like, comprising a cylinder, a piston movable therein and cooperable with the cylinder to provide a pressure space, a pressure reservoir connected with the pressure space and having a damping characteristic variable as a function of the position of the piston relative to the cylinder, a spring loaded pressure limiting valve located between the pressure space and the pressure reservoir, and opening towards the pressure reservoir, a spring abutment, and the tension of the spring being varied by displacement of the spring abutment corresponding to the relative movement between the piston and the cylinder, a piston rod for said piston, said pressure limiting valve being located within the interior of the cylinder and defined by a rod extending axially into the pressure space and constituting a valve seat with a further piston sliding in a space provided in the piston rod and loaded by said spring biased between the abutment and the further piston said further piston having an axial orifice, with said pressure reservoir being connected with a zone encompassing said further piston and spring loading said further piston, and said rod extending axially into the pressure space being displaceably secured in a base of the cylinder.

2. A line of movement dependent damping assemblage for hydropneumatic oleo struts and the like, comprising a cylinder, a piston movable therein and cooperable with the cylinder to provide a pressure space, a pressure reservoir connected with the pressure space andhaving a damping characteristic variable as a function of the position of the piston relative to the cylinder, a spring loaded pressure limiting valve located between the pressure space and the pressure reservoir, and opening towards the pressure reservoir. a spring abutment, and the tension of the spring being varied by displacement of the spring abutment corresponding to the relative movement between the piston and the cylinder, a piston rod for said piston, said pressure limiting valve being located within the interior of the cylinder and defined by a rod extending axially into the pressure space and constituting a valve seat with a further piston sliding in a space provided in the piston rod and loaded by said spring biased between the abutment and the further piston, said further piston having an axial orifree, with said pressure reservoir being connected with a zone encompassing said further piston and spring loading said further piston, and a plug for the lower end of the piston rod constitutes the abutment for the spring loading said further piston and is displaceable relative to the piston rod.

3. The damping assemblage as claimed in claim 2 in which said piston stroke is limited by a shoulder provided in the piston rod.

4. The damping assemblage as claimed in claim 3 in which said spring is pretensioned whence said further piston bears against said shoulder.

5. The damping assemblage as claimed in claim 4 in which said rod extending axially into the pressure space is provided with a reduced end portion which fits into the orifice of said further piston. 

